Retatrutide kidney function, in short: studies found less protein leaking into urine, and higher estimated kidney filtering in some groups. But in the first trial in people with kidney disease, reported in October 2026, directly measured filtering didn't significantly change over 24 weeks. Kidney protection isn't proven, and retatrutide isn't FDA-approved.
What can change that answer for you: advanced kidney disease (people below an eGFR of 25 weren't in that trial), dialysis or a kidney transplant, dehydration from vomiting or diarrhea, and any product that didn't come from a Lilly trial.
Here's the catch most pages miss. The kidney number on a normal lab report went up in some study groups. But the direct test in the CKD trial didn't show a significant improvement. The table below shows every result side by side, so you can tell a promising sign from a proven benefit.
Does retatrutide help or hurt kidney function?
The answer depends on what was measured. Retatrutide lowered protein in the urine and raised estimated filtering in some groups. But in the 24-week TRANSCEND-CKD trial, directly measured filtering was not significantly different from placebo, and no completed trial has shown that it prevents kidney failure or dialysis. A larger outcomes trial is still running.
In one line each:
- Promising: less albumin (a blood protein) leaking into urine in certain doses and groups studied so far.
- Not shown: a significant gain in measured filtering at 24 weeks in people with kidney disease.
- Unknown: whether it lowers the risk of kidney failure, dialysis, or kidney decline over years.
The retatrutide kidney studies, side by side
Results are compared with placebo. Each row shows who was studied, when, which test, and the source. Checked October 26, 2026.
| Study and who was in it | When | Test | Result vs. placebo | How to read it | Source |
|---|---|---|---|---|---|
| TRANSCEND-CKD — 146 adults with overweight or obesity and chronic kidney disease (eGFR 25–75), with or without type 2 diabetes | Week 24; presented Oct 22, 2026 | Measured GFR (direct test, main goal of the trial) | −1.4 mL/min/1.73 m² (95% CI −9.2 to +6.3; p = 0.714) | No statistically significant difference detected. The interval still allows benefit or harm; the trial is too short to settle long-term effects. | ASN abstract TH-PO1238 |
| Same trial, 42 people (29%) who started with UACR of 30 mg/g or more | Week 24 | UACR (protein in urine) | 49.2% lower (95% CI −70.6% to −12.3%) | A statistically significant drop in a kidney-damage marker, in this subgroup only. It does not mean 49% less kidney failure. | ASN abstract |
| Same trial, all participants | Week 24 | eGFR (estimate from creatinine and from cystatin C) | Higher than placebo (the accessible abstract text does not give exact amounts) | The estimates rose while the direct test didn't. Read them together. | ASN abstract |
| 2025 analysis, type 2 diabetes trial — 281 adults; mostly normal kidneys (average eGFR 91, median UACR 13 mg/g) | Week 36 | UACR | 37.0% lower at 12 mg (95% CI −57.3% to −7.0%) | A signal, not proof of fewer kidney failures. A research dose, not a recommended one. | Kidney Int Rep, 2025 |
| Same diabetes trial | Week 36 | eGFR | No change vs. placebo (after an early dip around week 12) | The estimate didn't improve in this group. | Full paper |
| 2025 analysis, obesity trial (no diabetes) — 338 adults; average eGFR 90, median UACR 7 mg/g | Week 48 | UACR | 28.0% lower at 8 mg; 31.5% lower at 12 mg | Most people started with normal urine protein, so the real-world drop was small. | Kidney Int Rep, 2025 |
| Same obesity trial | Week 48 | Creatinine eGFR | +5.3 (8 mg) and +8.5 (12 mg) mL/min/1.73 m² | An estimate, not a direct measurement. Not proof that kidney function was "restored." | Full paper |
| TRIUMPH-Outcomes — goal of 10,000 adults 45+ with heart disease and/or kidney disease | Runs through Feb 2029 | Serious heart events and worsening kidney function | No results yet | This is the trial built to answer the question that matters most. | Lilly trial page |
Three things to know about this evidence:
- The 2025 numbers are a look-back. The researchers re-analyzed one diabetes trial and one weight-loss trial that weren't designed to study kidneys. Only about 1 in 20 people in them had reduced kidney function (eGFR under 60).
- The 2026 numbers are a conference poster. TRANSCEND-CKD was presented at ASN Kidney Week in Denver. It has not yet appeared as a full peer-reviewed results paper.
- Lilly funded all of it. That's normal for a drug in development, but it's worth knowing. We didn't redo their math; we read their reports.
Why can estimated kidney function rise when measured function doesn't?
eGFR and measured GFR describe the same kidney job, but they get the number in different ways. eGFR is calculated from blood markers like creatinine, which can shift for reasons besides the kidneys. Measured GFR tracks a test substance the kidneys clear, so it's closer to the real thing.
Think of it like a car's speed. eGFR is guessing speed from how far you got. Measured GFR is the radar gun.
Four kidney measurements, four different questions
| Number on your report | What it is | What it did on retatrutide | What it can't tell you alone |
|---|---|---|---|
| eGFR from creatinine (mL/min/1.73 m²) | An estimate of filtering, calculated from creatinine, a waste product partly made by muscle | Rose in the obesity trial and in TRANSCEND-CKD | The National Kidney Foundation notes creatinine is affected by muscle size and diet. Big body changes can move it. |
| eGFR from cystatin C | A second estimate, from a different blood protein | Also rose in TRANSCEND-CKD | Still an estimate, not a direct test |
| Measured GFR | A direct test using a substance like iohexol that the kidneys clear | No significant change in TRANSCEND-CKD | Rarely done outside research. One 24-week trial can't settle long-term risk. |
| UACR (mg/g) | How much albumin leaks into urine, compared with creatinine | Fell in certain dose groups and the 2026 subgroup with high starting UACR | A drop is good news, but it isn't proof of fewer kidney failures |
Why the gap between the estimates and the direct test? The abstract doesn't settle it. One known factor is that creatinine depends partly on muscle, and big weight loss changes body makeup. It's also possible the estimates are partly picking up something real. Honest answer: for that 24-week kidney trial, the direct test is the stronger filtration measure, and it found no clear difference from placebo.
Here's a hypothetical. Say you lose 40 pounds and your eGFR goes from 62 to 70. That could be good news. It could also be partly a lab effect. A clinician can sort it out, sometimes with a cystatin C test or by watching the trend over time. For more on reading these numbers, see eGFR and kidney outcomes explained and why weight loss changes muscle on retatrutide.
What does less protein in urine mean?
A lower UACR means less albumin is leaking into the urine. That's generally a good sign. But a leak marker tells you about the leak, not everything about the filter.
The National Kidney Foundation says a normal UACR is under 30 mg/g. One high result isn't a diagnosis. The test is repeated, and two high results over three months or more point to kidney disease.
That's why the 2025 drops matter less than they sound. Most people in those trials already had normal levels, so a 30% drop from a normal number is a small change in real life.
What you can and can't say about retatrutide and your kidneys
Headlines and online posts often stretch these results. Here's what the evidence supports today.
| Claim you might see | True? | Why |
|---|---|---|
| "Retatrutide lowered protein in the urine." | Yes, in studied groups | Shown in the 2025 analyses and the 2026 CKD trial |
| "Retatrutide raised eGFR." | Yes, in some groups, as an estimate | Obesity trial and TRANSCEND-CKD; not the diabetes trial |
| "Retatrutide improves kidney function in CKD." | Not shown | The direct test didn't change significantly at 24 weeks (p = 0.714) |
| "Retatrutide cuts kidney failure risk by 49%." | No | 49.2% was a urine-protein drop in a 42-person subgroup, not kidney failure |
| "Retatrutide is safe with stage 4 CKD, dialysis, or a transplant." | Not known | TRANSCEND-CKD allowed eGFR as low as 25 (the upper part of stage 4 CKD), but did not establish safety for stage 4. Dialysis and transplant patients weren't included. |
| "People with kidney disease can take it at a certain dose." | No | There's no approved product, label, or dose |
Can retatrutide hurt your kidneys?
The trials so far haven't shown a pattern of kidney harm, but they don't prove it's free of kidney risk either. A few kidney-related problems were reported in both the retatrutide and placebo groups. The studies were too small and short to tell any one person with kidney disease that retatrutide is safe.
Here's every kidney-related event the 2025 analysis reported. These are events that happened during the trials, not proof the drug caused them.
| Trial | What was reported | What it doesn't prove |
|---|---|---|
| Type 2 diabetes trial | 1 serious acute kidney injury (in a placebo patient); 1 mild kidney impairment (retatrutide 12 mg); 1 moderate dehydration (retatrutide 8 mg) | That retatrutide has zero kidney risk, or what your personal risk is |
| Obesity trial | 1 serious acute kidney injury (retatrutide 8 mg), which researchers noted was possibly linked to a COVID-19 infection | That retatrutide did or didn't contribute |
| Obesity trial | 3 chronic kidney disease or kidney failure events (1 placebo, 2 retatrutide); 4 dehydration events (3 retatrutide, 1 placebo) | A real-world rate, especially for people with serious kidney disease |
Source: Heerspink et al., Kidney International Reports, 2025.
There was also an early dip. In the diabetes trial, eGFR fell a bit around week 12, then came back to where it started by week 36. That's a trial average, though. Don't assume your own lab change is the same kind of dip without a clinician.
Why vomiting and dehydration matter
Retatrutide's most common side effects are nausea, vomiting, and diarrhea, especially as the dose goes up. If you lose more fluid than you take in, less blood reaches your kidneys, and they can struggle. For approved drugs in this family, the FDA labels carry a warning about kidney injury from dehydration. Retatrutide has no label yet, so that warning doesn't exist for it in writing. The risk doesn't go away just because the label doesn't exist. See retatrutide side effects for the full list by dose.
Get medical care today if you: can't keep fluids down, are peeing much less than usual, have dark urine, feel dizzy or faint when you stand, or feel confused or very weak. Call 911 for fainting, trouble breathing, or anything that feels like an emergency. If you've been told to limit fluids because of kidney or heart disease, ask your care team before drinking more.
What if your creatinine rose or eGFR fell after using "reta"?
A changed kidney lab needs a clinician, not a guess. It could be dehydration, an early dip, another medicine, an illness, or the product itself. A blood test alone can't tell you which.
If you used something sold online as retatrutide, tell your doctor exactly that. The trial results above came from Lilly's tested drug at known doses with regular lab checks. A "research use only" vial doesn't come with any of that, and it may not even contain what the label says. Something like this works:
"I've been using a product sold as retatrutide. I'm not sure what's in it. I started around [date] and last took it on [date]. Here are my symptoms and my latest labs."
Don't change other prescribed medicines or start a hydration plan on your own. Let your care team decide.
Can retatrutide cause kidney stones or kidney pain?
There's no published kidney stone rate for retatrutide that we could find. STAT reported in February 2025 that one trial participant who lost 30% of his weight developed a kidney stone. It isn't known whether the drug caused it. Research on stones and the wider GLP-1 drug family is mixed, and none of those other-drug studies can settle retatrutide's stone risk.
- One report, not a rate. The STAT story described a single participant. One case can't tell you how often something happens.
- Mixed research on GLP-1 drugs. A large Veterans Affairs study reported an association between GLP-1 drugs and more kidney stones. But a 2025 ASN study of semaglutide versus metformin found no significant difference in stone diagnoses. A separate urine-chemistry study looked at stone-risk markers, not stone events. None studied retatrutide, so none proves its stone risk.
Is it your kidney or your back? Your kidneys sit in your back, just under your ribs. According to NIDDK, a stone can cause sharp pain in your back, side, lower belly, or groin, along with blood in your urine, cloudy or bad-smelling urine, fever, or chills. NIDDK says to see a health care professional right away if you have these symptoms. Pain with fever could also mean a kidney infection, which needs prompt care.
NIDDK's general prevention advice is to drink plenty of water unless a health care professional tells you otherwise. That "unless" matters for anyone with kidney disease.
Can you take retatrutide if you have kidney disease?
Not as a normal prescription. Retatrutide isn't approved by the FDA for any use. Lilly's public guidance points people to its clinical trials, but a narrow, doctor-requested expanded access pathway is also listed for certain adults who can't join a trial. Kidney disease alone doesn't qualify anyone.
There are three very different paths you might hear about:
- Clinical trials. Strict rules, specific sites, and you might get placebo. See our retatrutide clinical trials tracker.
- Expanded access. This is not open enrollment. The ClinicalTrials.gov listing (NCT07629401) is for adults with BMI 35 or higher, at least two serious or life-threatening obesity-related complications under ongoing care, continued obesity despite taking and tolerating the highest available dose of approved long-term weight-management treatment, and no access to a suitable trial. Standard options, including surgery, must have been discussed. Your treating doctor—not you—must ask Lilly, and supply, location, and an individual review still matter. Details are in retatrutide early access.
- Online sellers and "research" vials. Not legitimate. The FDA says retatrutide can't be used in compounding under federal law. It has also warned companies selling it labeled "for research purposes," and Lilly warns consumers not to buy products marketed as retatrutide online. More in compounded retatrutide and how to avoid fake GLP-1s.
There's also no approved retatrutide dose, and no kidney dose adjustment to follow. Any chart you find online is guesswork.
Who has been studied, and who hasn't
| Group | Studied? |
|---|---|
| Overweight or obesity with kidney disease, eGFR 25–75 | Yes — TRANSCEND-CKD, 24 weeks |
| Type 2 diabetes or obesity with mostly normal kidneys | Yes — the 2025 analyses |
| Type 2 diabetes with moderate or severe kidney impairment (eGFR 15 to under 60) | Trial underway, no results yet (see below) |
| Stage 4 CKD (eGFR 15–29) | Trial eligibility covered 25–29, but a stage-4 safety result was not reported |
| eGFR under 25 | Not in TRANSCEND-CKD |
| Dialysis | Not studied in the trials above |
| Kidney transplant | Not studied; excluded from TRIUMPH-Outcomes |
| Living kidney donors | No data we could find |
Kidney trials still running
| Trial | Who and what | Where it stands (checked Oct 26, 2026) | Don't assume |
|---|---|---|---|
| TRANSCEND-T2D-3 | Type 2 diabetes on basal insulin, eGFR 15 to under 60; blood sugar control and safety | Enrollment completed; listed through November 2026 | That a kidney dose is safe before results post |
| TRIUMPH-Outcomes | Adults 45+, BMI 27+, heart disease and/or kidney disease; serious heart events and kidney decline | Listed through February 2029 | That the drug works because a big trial exists |
What's proven for kidneys today
Retatrutide is an experimental drug, and kidney results from other drugs don't carry over to it. Among drugs available now, Ozempic injection (semaglutide) is the only GLP-1 with an FDA-approved kidney use, for adults with type 2 diabetes and chronic kidney disease. That's a different drug with a completed kidney outcomes trial.
| Ozempic injection (semaglutide) | Tirzepatide (Mounjaro, Zepbound) | Retatrutide | |
|---|---|---|---|
| FDA-approved? | Yes | Yes | No |
| FDA-approved kidney use? | Yes — adults with type 2 diabetes and CKD | No | No (no label at all) |
| Best kidney evidence | A completed kidney outcomes trial (FLOW) | A 2026 exploratory kidney-outcomes analysis showed fewer composite kidney events vs. dulaglutide; no kidney indication on the FDA labels | Look-back analyses and one 24-week poster |
| Can you get it today? | Yes, with a prescription | Yes, with a prescription | Only through a trial or narrow expanded access |
That tirzepatide finding came from adults with type 2 diabetes and heart disease. It was an exploratory comparison with dulaglutide, not an FDA kidney approval and not evidence for retatrutide.
If you have kidney disease, don't put care on hold waiting for retatrutide. Ask your kidney and diabetes clinicians which treatments with proven kidney results fit you now. Our guide to GLP-1s and kidney disease walks through each approved drug's kidney label, and best GLP-1 for kidney disease compares them. If retatrutide's weight-loss results are what drew you in, see retatrutide alternatives you can get today.
If your kidney questions are settled with your doctor and you're comparing approved weight-management options, the right one depends on your state, your insurance and its drug list, a shot or a pill, and your budget. The RX Index's Find My GLP-1 Path tool walks you through a few quick questions and shows the GLP-1 paths and providers that fit your goals, budget, insurance, and situation. It's free, takes about 2 minutes, and needs no signup. It doesn't judge kidney safety.
What we actually verified
We checked the original sources ourselves. Here's exactly what we read, what we couldn't confirm, and what's still unknown.
The RX Index is the independent GLP-1 decision resource that scores telehealth providers and treatment paths on clinical legitimacy, care quality, transparency, access, and cost, so readers can choose the path that fits their situation.
Checked October 26, 2026:
- The ASN Kidney Week 2026 abstract for TRANSCEND-CKD (poster presented October 22, 2026; Lilly-funded).
- The 2025 Kidney International Reports analysis, including its kidney safety events and limits.
- Lilly's trial pages for TRANSCEND-T2D-3 and TRIUMPH-Outcomes, and ClinicalTrials.gov records.
- The FDA's page on unapproved GLP-1 drugs (content current as of October 1, 2026) and Lilly's retatrutide fact page.
- The current Ozempic, Mounjaro, and Zepbound prescribing labels, and the 2026 SURPASS-CVOT kidney analysis.
- National Kidney Foundation and NIDDK pages on eGFR, UACR, and kidney stones.
What we couldn't verify: exact eGFR amounts from TRANSCEND-CKD (the accessible abstract text gives only the direction of the change), any long-term kidney benefit, and a safe retatrutide dose for anyone with kidney disease. We didn't test any product, run labs, or review patient records. Our methodology explains how we work.
Still unknown: whether retatrutide slows kidney disease over years, whether measured filtering stays steady with longer use, and how it behaves in severe kidney disease, dialysis, or after a transplant.
Retatrutide kidney function FAQ
Can retatrutide cause kidney problems?
The trials haven't shown a pattern of kidney harm, but a few kidney-related events happened, including one serious acute kidney injury in a retatrutide patient that researchers said was possibly linked to COVID-19. The biggest known risk for drugs in this family is dehydration from vomiting or diarrhea. Call your clinician if you can't keep fluids down or you're peeing much less.
Does retatrutide improve kidney function?
Some kidney markers improved, especially protein in the urine and estimated filtering in certain groups. But in the 2026 trial in people with kidney disease, directly measured filtering didn't significantly change after 24 weeks. Long-term kidney protection isn't proven.
Can I take retatrutide if I have chronic kidney disease?
Not as a normal prescription. It isn't FDA-approved. Trials are the main legitimate route, and a narrow doctor-requested expanded access program is listed for certain adults with severe obesity and serious complications who can't join a trial. Ask your kidney care team about treatments with proven kidney results in the meantime.
Why did my eGFR go up on retatrutide?
It could be a real change or partly a lab effect. eGFR is calculated from creatinine, which depends partly on muscle, and big weight loss changes body makeup. In TRANSCEND-CKD, eGFR estimates rose while the direct test showed no significant improvement, so ask your clinician how to read your trend.
Why did my creatinine go up?
Common reasons include dehydration, a recent illness, other medicines, an early dip after starting this kind of drug, or a real kidney problem. A blood test alone can't tell which. Contact your prescriber, especially if you also have vomiting, dizziness, or less urine.
Does retatrutide cause kidney stones?
There's no published stone rate for retatrutide. STAT reported one trial participant who developed a stone after losing 30% of his weight, but the cause wasn't known. See a health care professional right away for sharp back or side pain, blood in your urine, or fever.
Did retatrutide reduce protein in the urine?
Yes. In the 2026 kidney trial, urine protein (UACR) dropped 49.2% compared with placebo in the 42 people who started with elevated levels. That's a good sign for a kidney-damage marker, but it doesn't mean 49% less kidney failure.
Is retatrutide safe after a kidney transplant or after donating a kidney?
The evidence doesn't answer that. Transplant patients weren't in these trials and are excluded from TRIUMPH-Outcomes, and we found no data on living donors. Ask your transplant or donor follow-up team rather than going by someone else's story online.
Does retatrutide need a dose change for kidney disease?
There's no approved retatrutide dose at all, so there's no kidney dose adjustment to follow. Any dosing chart from a seller is not a substitute for a licensed clinician.
Is retatrutide FDA-approved for kidney disease?
No. As of October 26, 2026, retatrutide isn't FDA-approved for kidney disease or anything else. The FDA says it can't be used in compounding under federal law.
When will we know if retatrutide protects the kidneys?
The TRIUMPH-Outcomes trial is testing serious heart events and worsening kidney function in up to 10,000 adults. Lilly lists it as running through February 2029, though timelines can change. Until results come out, kidney protection is an open question.
Should I wait for retatrutide if I have kidney disease?
No. Don't delay kidney care for an experimental drug whose approval and kidney benefit aren't guaranteed. Ask your kidney and diabetes clinicians which proven treatments fit you now.
Still not sure which GLP-1 path fits you? Take The RX Index's free Find My GLP-1 Path quiz — about 2 minutes, no signup.
Sources
All checked October 26, 2026.
- Heerspink HJL, et al. Effects of Retatrutide on Kidney Parameters in Participants with Obesity or Overweight and CKD (abstract TH-PO1238). ASN Kidney Week 2026 poster, October 22, 2026.
- Heerspink HJL, et al. The Effect of Retatrutide on Kidney Parameters in Participants With Type 2 Diabetes Mellitus and/or Obesity. Kidney International Reports, 2025 (full text).
- Heerspink HJL, et al. Rationale, design and baseline characteristics of the TRANSCEND-CKD trial. Nephrology Dialysis Transplantation, 2026 (design paper, not results).
- ClinicalTrials.gov: NCT05936151 (TRANSCEND-CKD), NCT06383390 (TRIUMPH-Outcomes), NCT07629401 (expanded access).
- Eli Lilly trial pages: TRANSCEND-T2D-3; TRIUMPH-Outcomes.
- Eli Lilly. What to know about retatrutide. Updated fall 2026.
- U.S. FDA. FDA's Concerns with Unapproved GLP-1 Drugs Used for Weight Loss. Content current as of October 1, 2026.
- National Kidney Foundation. Urine albumin-creatinine ratio (uACR); Estimated glomerular filtration rate (eGFR).
- NIDDK. Symptoms & Causes of Kidney Stones; Eating, Diet, & Nutrition for Kidney Stones.
- Chen E. How much weight loss is too much? STAT, February 20, 2025.
- The impact of SGLT2 inhibitors and GLP-1 receptor agonists on 24-hour urine parameters. Retrospective cohort study; urine chemistry, not actual stone diagnoses.
- U.S. prescription labeling (DailyMed): Ozempic injection (label updated June 2026), Mounjaro, and Zepbound. Indications and kidney injury from dehydration warnings checked October 26, 2026.
- Zoungas S, et al. Tirzepatide versus dulaglutide and major kidney events: prespecified exploratory SURPASS-CVOT analysis. The Lancet Diabetes & Endocrinology, July 2026. This is tirzepatide evidence, not retatrutide evidence.
- Mapping the effectiveness and risks of GLP-1 receptor agonists. 2025 Veterans Affairs observational analysis, including nephrolithiasis signals.
- Ganesan C, et al. GLP-1 Receptor Agonist Semaglutide and Risk of Incident Urinary Stone Disease. ASN Kidney Week 2025 abstract; no statistically significant stone association in semaglutide-versus-metformin matched cohort.
- National Kidney Foundation. Stage 4 chronic kidney disease. eGFR 15–29 mL/min/1.73 m².